Medical devices can be implanted in a body to perform tasks including monitoring, detecting, or sensing physiological information in the body, diagnosing a physiological condition or disease, treating a physiological condition or disease, or restoring or otherwise altering the function of an organ or a tissue. Examples of an implantable medical device can include a cardiac rhythm management device, such as a pacemaker, a cardiac resynchronization therapy device, a cardioverter or defibrillator, a neurological stimulator, a neuromuscular stimulator, or a drug delivery system. Implantable medical devices can include a telemetry circuit configured to provide wireless communication between the implantable medical device and an external device, e.g., to send information (such as physiological information) from the implantable medical device to the external device, or to receive information (e.g., such as programming instructions) at the implantable medical device from the external device.